Peroneus quartus muscle: A case report and review of the literature

The peroneus quartus is a supernumerary muscle of the lateral compartment o f the lower leg. There are several variations of this accessory muscle, and its terminology is very confusing. The peroneus quartus is found with a frequency varying from 10 to 21.7% of observed individuals.(4,17) It is rarely involved in pathologic processes o f the foot and ankle. Only a few reports exist in the literature involving peroneus quartus in a "retromalleolar conflict" (lateral ankle stenosis(17) ), sometimes in association with longitudinal attrition and tears of the pe roneus brevis. We present a novel case, together with a review of the clini cal, anatomic, and radiologic references about this muscle, and we try to m ake order in classification and terminology of its different forms.